The concept of crystallization-induced reaction was applied to the ester interchange reaction of copolyester in the solid-state. Two types of copolyesters were employed in this study, namely: (1) poly(cis/trans 1,4-cyclohexylenedimethylene terephthalate) -- a copolyester with both comoners cocrystallizable in the same crystal lattic, and (2) poly(ethylene terephthalate/2-methylsuccinate) -- a copolyester which contains only one type of crystallizable monomer units (ethylene terephthalate repeating unit).